Corn plastic no answer

The downsides are many to this supposed green-friendly substitute

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This cup is made of PLA, a plastic made from cornstarch.

PHOTO COURTESY OF BEC/FLICKR

What are the environmental pros and cons of corn-based
plastic as an alternative to conventional petroleum-based plastic? Polylactic acid, a plastic substitute made from
fermented plant starch (usually corn) is quickly becoming a popular
alternative to traditional petroleum-based plastics. As more and more
countries and states follow the lead of China, Ireland, South Africa,
Uganda, and San Francisco in banning plastic grocery bags, responsible for
so much so-called “white pollution” around the world, PLA is
poised to play a big role as a viable, biodegradable replacement. Proponents also tout the use of PLA — which is
technically “carbon neutral” in that it comes from renewable,
carbon-absorbing plants — as yet another way to reduce our emissions
of greenhouse gases in a quickly warming world. PLA also will not emit
toxic fumes when incinerated.But critics say that PLA is far from a panacea for the
world’s plastic-waste problem. For one thing, although it does
biodegrade it does so very slowly. According to Elizabeth Royte, writing in
Smithsonian, PLA
may well break down into its constituent parts (carbon dioxide and water)
within three months in a “controlled composting environment”
— that is, an industrial composting facility heated to 140 degrees
Fahrenheit and fed a steady diet of digestive microbes — but it will
take far longer in a compost bin or in a landfill packed so tightly that no
light and little oxygen are available to assist in the process. Indeed,
analysts estimate that a PLA bottle could take anywhere from 100 to 1,000
years to decompose in a landfill. Another issue with PLA is that, because it is of
different origin than regular plastic, it must be kept separate when
recycled, lest it contaminate the recycling stream. Being plant-based, PLA
needs to be sent to a composting facility, not a recycling facility, per
se, when it has served its usefulness, and that points to another problem:
Right now there are only 113 industrial-grade composting facilities across
the U.S. Another downside of PLA is that it is typically made
from genetically modified corn, at least in the U.S. The largest producer
of PLA in the world is NatureWorks, a subsidiary of Cargill, which is the
world’s largest provider of genetically modified corn seed. With
increasing demand for corn to make ethanol fuel let alone PLA, it’s
no wonder that Cargill and others have been tampering with genes to produce
higher yields, but the future costs to the environment and human health of
genetic modification are still largely unknown and could be very high. Although PLA holds promise as an alternative to
conventional plastic once the means of disposal is worked out, grocery
shoppers would do well to simply switch to reusable containers, from cloth
bags, baskets, and backpacks for grocery shopping (most chains now sell
canvas bags for less than a dollar apiece) to safe, reusable (nonplastic)
bottles for beverages. As for other types of PLA items — such as
those plastic “clamshells” that hold cut fruit (and a host of
industrial and medical products are now made from PLA) — there is no
reason to pass them by, but until the kinks are worked out on the disposal
and reprocessing end PLA may not be much better than the plain old plastic
it’s designed to make obsolete. For more information:
NatureWorks, www.natureworksllc.com; Smithsonian’s “Corn Plastic to the Rescue,”
www.smithsonianmag.com/science-nature/plastic.html.Send questions to Earth Talk at P.O. Box 5098,
Westport, CT 06881 or e-mail earthtalk@emagazine.com.